Digital Watershed Model Of Yellow River

The digital watershed model can simulate processes of rain-runoff, soil erosionand sediment transport in a large river basin. It is very useful for flood control, waterresources management and soil conservation. Up to date, previous efforts on digitalwatershed models have been focused on small river basins or catchments such thatthe developed models could not effectively simulate hydrological processes in a largeriver basin. The objective of the dissertation is to develop an integrated digitalwatershed model system which incorporates all hydrological processes into aframework.The digital watershed model has been developed based on Digital ElevationModel (DEM) data management system. The whole river basin is classified into fourlevels. At the first level routing processes in main channels are simulated for thewhole watershed;at the second level routing processes in minor streams arecalculated for the sub-basin area;at the third level hydrological processes aresimulated for the small sub-catchment unit, which consists of surface runoffgeneration units and drainage trenches. At the fourth level surface rain-runoff and soilerosion models were developed for the hillslope unit. The models for these four levelsare integrated into a framework. Five key issues were explored for developing thedigital watershed modeling system, including DEM data management for a largewatershed, parameters extraction of stream networks, model-parameters extractionfrom emote sensing images, rainfall data acquisition, and parallel computation of theconcurrent computer group. The developed modeling system was verified with theobservation data from the Chabagou, a small sub-basin of the Yellow Rive. Theefficiency coefficient was 75%.The developed digital watershed model was applied for simulating the waterresources distribution of the region from the upper Yellow River to the Huayuankoustation. The errors between simulated and observed results were acceptable. Thedeveloped digital watershed model was also applied to compute the runoff andsediment production for the sandy and grit area in the flood season of year 1967, 1978,1983, 1994 and 1997. The result shows that the quantity, distribution and density ofthe rainfall as well as the size of the sediment are greatly affect the sediment load thatenters into the channel of the Yellow River. The simulated results can well explain thephenomenon of "high water and low sediment" or "low water and high sediment" inthe Yellow River. The application of the developed digital watershed model in theXiaolangdi to Huayuankou Reach of the Yellow River shows that the simulationtime-step of the model can be adjusted to meet with different computationrequirements: short time-step (6 min) for event-based streamflow simulation and longtime-step (1 hour) for continuous-precipitation-based streamflow simulation.Combined with the rainfall-predict module, the model can be used for floodprediction.In general, the developed digital watershed model in this study could be used forrain-runoff simulation and water resources estimation of a whole watershed with largescale. The simulation results in the sandy and grit area in the Loess Plateau cansupply decision support for check-dams planning.